Hydraulically expanded hubs are well known to the prior art. Such hubs operate upon the principle of expanding the diameter of the hub by application of hydraulic pressure to the interior surface of the hub so as to enable the expanded hub to slide over the surface of a shaft. The hydraulic pressure is applied through a chamber defined between a groove in the interior of the hub and the outside diameter of the shaft over which the hub is to slide. Upon removal of the pressure, the hub contracts and conforms to the diameter of the arbor or shaft, thereby frictionally securing the hub to the shaft. This type of hydraulic hub is disclosed for example in British Patent No. 1,574,421 wherein the hub has a conventional slitting knife secured thereon.
Another patent which discloses a similar hydraulic hub and a method for starting the hub onto a shaft is U.S. Pat. No. 4,541,163. This patent is assigned to the assignee of this application and the disclosure of this patent is hereby incorporated by reference for purposes of completing the disclosure of a hub and shaft of the type to which this invention is applicable. According to the disclosure of this patent, after the hub is started onto the shaft, hydraulic pressure is applied to the interior of the hub through a groove on the interior of the hub. While the hub is expanded by the hydraulic pressure, it is axially moved and positioned on the shaft. After the hub has been moved to its ultimate axial position, which is typically determined by tolerances as close as 0.001", the hydraulic pressure is removed to lock the hub to the shaft at the new position.
For some applications a problem occurs when the hydraulic fluid used to expand the hub leaks from between the hub and the outside diameter of the shaft during the positioning of the hub on the shaft. This oil, while minimal in quantity, adheres to the shaft and may, during subsequent rotation of the shaft, be distributed over a work area by centrifugal force resulting from rotation of the shaft. Part of this oil may be splattered onto a workpiece or material to be worked by the tool connected to the hub. When the material to be worked is one which must be absolutely free of oil, as for example, a sheet of metal used to fabricate cans for the food industry, this oil contamination is a very serious problem.
Currently, to prevent the contamination of such work material surfaces, meticulous cleaning of the shaft must be performed after positioning of the hub, to remove all vestiges of oil from the shaft. This process is quite time consuming and adds additional labor to the process of moving the hydraulic hub from one position along the shaft to another. Furthermore, careful attention must be observed in the removal of the oil from the shaft to prevent any possible contamination of a workpiece from occurring.
It has therefore been an objective of this invention to prevent the laborious and time consuming process of removing oil from a shaft after axial positioning of a hydraulic hub on the shaft.
It has been a further objective of the present invention to prevent the contamination of workpieces resulting from splattering of oil from a shaft upon which hydraulic hubs have been positioned.